Sector-specific network configuration

Abstract

According to an aspect, there is provided a computer- implemented method as follows. A first sector of a first cellular communication network using a first radio access technology, RAT, is determined. The first sector supports a first low frequency band and has a neighboring cell supporting a high frequency band but not the first low frequency band. One or more measurement reports of a second cellular communication network using a second RAT are obtained. Each measurement report comprises results for a second sector corresponding to the first sector. Based thereon, one or more first reference signal received power, RSRP, distributions for a second low frequency band at the second sector are calculated. A sector-specific received signal strength threshold for triggering inter frequency measurements is calculated based on the one or more first RSRP distributions. An access node is configured to use the sector-specific received signal strength threshold in the first sector.

Description

SECTOR-SPECIFIC NETWORK CONFIGURATIONTECHNICAL FIELD

[0001] Various example embodiments relate to cellular communications.BACKGROUND

[0002] A frequency layer refers to a specific frequency band or range within which communication signals are transmitted and received in given wireless communication network (e.g., a mobile network). In a typical mobile network such one based on Long-Term Evolution (LTE) or Fifth Generation New Radio (5G NR) standard, several frequency layers may be in use simultaneously. These frequency layers may typically comprise at least one “low” band frequency layer (corresponding, e.g., to an LTE 800 or NR 700 frequency band) and / or or at least one “high” band frequency layer (corresponding, e.g., to an LTE 2600 or NR 3500 frequency band).

[0003] A layering strategy defines how terminal devices (equally called user equipment, UE) are moved between the frequency layers. A layering strategy may depend, e.g., on priorities and / or power levels of the different frequency layers. In a homogeneous mobile network with continuous frequency layers, implementing a certain defined layering strategy is a relatively straightforward task as a single parameter set can be used across the whole mobile network. The problem becomes more complicated when the mobile network is non-homogeneous, i.e., when the frequency layers are no longer continuous across the mobile network.SUMMARY

[0004] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification thatdo not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0005] According to a first aspect of the present disclosure, there is provided a computer-implemented method comprising: determining a first sector of a first cell of a first cellular communications network which uses a first radio access technology, RAT, wherein the first sector supports at least a first low frequency band of the first RAT and has at least one neighboring cell of the first cellular communications network supporting a high frequency band of the first RAT but not supporting the first low frequency band, the first low frequency band being defined as a frequency band existing at lower frequencies compared to the high frequency band; obtaining one or more measurement reports of a second cellular communications network which uses a second RAT, wherein each of the one or more measurement reports comprises at least results of radio measurements for a second sector of a second cell being a sector of the second cellular communications network corresponding most closely in terms of location, antenna bearing and supported low frequency band to the first sector; calculating one or more first reference signal received power, RSRP, distributions for a second low frequency band of the second RAT at the second sector based on the one or more measurement reports; calculating, at least based on at least some of the one or more first RSRP distributions, a sector-specific received signal strength threshold for triggering inter frequency measurements at the first sector of the first cell, wherein the sector-specific received signal strength threshold is defined to be at least higher than a corresponding global threshold currently in use in the first sector; and causing configuring an access node serving the first cell at least to use the sector-specific received signal strength threshold for triggering inter frequency measurements in the first sector.

[0006] According to a second aspect of the present disclosure, there is provided an apparatus comprising means for performing the computer-implemented method according to the first aspect.

[0007] According to a third aspect of the present disclosure, there is provided an apparatus comprising at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform the computer-implemented method according to the first aspect.

[0008] According to a fourth aspect of the present disclosure, there is provided a computer program which, when the computer program is executed by a computing device, causes the computing device to carry out at least the computer-implemented method according to the first aspect.

[0009] According to a fifth aspect of the present disclosure, there is provided a non- transitory computer readable medium comprising program instructions that when executed by an apparatus, cause the apparatus to perform at least the computer-implemented method according to the first aspectBRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figures 1 & 2 illustrate a system to which a process according to some embodiments may be applied;

[0011] Figures 3 to 7 illustrate processes according to some embodiments;

[0012] Figure 8 illustrates pre-drive time series throughput in a pilot cluster for a 5G non-standalone (NS A) mobile network and a standalone (SA) mobile network;

[0013] Figure 9 illustrates post-drive time series throughput in a pilot cluster for a 5G NS A mobile network and a SA mobile network;

[0014] Figure 10 illustrates a cumulative distribution function (CMF) of downlink (DE) throughput when using the method according to an embodiment (“After CDF”) and without using the method according to the embodiment (“Before CDF”); and

[0015] Figure 11 illustrates an apparatus according to some embodiments.DETAIEED DESCRIPTION OF SOME EMBODIMENTS

[0016] The following embodiments are only presented as examples. Although the specification may refer to “an”, “one”, or “some” embodiment(s) and / or example(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s) or example(s), or that a particular feature only applies to a single embodiment and / or example. The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recitedfeatures. Single features of different embodiments and / or examples may also be combined to provide other embodiments and / or examples.

[0017] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0018] As used in connection with embodiments, the terms “low frequency band” and “high frequency band” (associated with a particular radio access technology) are to be understood as two (radio) frequency bands where the low frequency band exists at lower frequencies compared to the high frequency band. The same applies for “first low frequency band” and “high frequency band” and for “second low frequency band” and “high frequency band”. The “first low frequency band”, “high frequency band” and “second low frequency band” may be equally called first, second and third frequency bands, respectively. The lowest frequency of the high frequency band may be larger than the highest frequency of the (first and / or second) low frequency band. In some embodiments, the lowest frequency of the high frequency band may be larger than the highest frequency of the (first and / or second) low frequency band times two. In some embodiments, the (first and / or second) low frequency band may exist at frequencies lower than 1 GHz or at least lower than 2 GHz. In some embodiments, the high frequency band may exist at frequencies higher than 1 GHz or alternatively higher than 2 GHz or even higher than 3 GHz. It should be emphasized that, in connection with embodiments, a (first and / or second) low frequency band does not refer to the Low Frequency (LF) band as designated by the International Telecommunication Union (ITU), a medium frequency band does not refer to the Medium Frequency (MF) band as designated by the ITU, and a high frequency band does not refer to the High Frequency (HF) band as designated by the ITU.

[0019] In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communication networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are theuniversal mobile telecommunications system (UMTS) radio access network (UTRAN or E- UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad- hoc networks (MANETs), Internet Protocol multimedia subsystems (IMS), rebel SIM (R- SIM) for code division multiple access (CDMA) technologies such as lx and lx evolution data optimized (IxEV-DO), global system for mobile communications (GSM) or any combination thereof.

[0020] In the following, an A2 event may be defined as handover measurement event for a terminal device in a 5G NR cellular communication network (or a 5G NR mobile network) which is triggered when a signal quality (e.g., received signal strength or signal- to-interference-plus-noise ratio) of a serving cell (or a special cell, SpCell) falls below a certain threshold (so-called A2 threshold). When the A2 event is triggered, the network evaluates a suitability of a neighboring cell (or a particular sector thereof) for handover based on its signal quality compared to the signal quality of the serving cell. After the A2 event is triggered, the terminal device may be configured with a measurement gap and an A5 event for inter-frequency handover. Due to this measurement gap during which the terminal device is unable to receive or transmit data, the inter-frequency measurements should typically be started as late as possible (i.e., the A2 threshold should be as low as possible).

[0021] In the following, an A3 event may be defined as handover measurement event for a terminal device in a 5G NR cellular communication network (or a 5G NR mobile network) which is triggered when a signal quality (e.g., received signal strength or signal- to-interference-plus-noise ratio) of a serving cell (or a special cell, SpCell) exceeds a signal quality of a neighboring cell by a certain hysteresis margin (i.e., a certain offset). The A3 event helps in preventing unnecessary handovers due to small fluctuations in signal quality. When the A3 event is triggered, the network may reassess whether handover to the neighboring cell is necessary based on hysteresis criteria.

[0022] In the following, an A4 event may be defined as a handover measurement event for a terminal device in a 5G NR cellular communication network (or a 5G NR mobile network) which is triggered when a signal quality (e.g., received signal strength or signal- to-interference-plus-noise ratio) of a neighbor cell (or a special cell, SpCell) exceeds athreshold (a so-called A4 threshold). The A4 event may be used, e.g., for handover procedures which do not depend upon the coverage of the serving cell.

[0023] In the following, an A5 event may be defined as a handover event for a terminal device in a 5G NR cellular communication network (or a 5G NR mobile network) which is triggered when a signal quality (e.g., received signal strength or signal-to-interference-plus- noise ratio) of a serving cell (or a special cell, SpCell) falls below a first threshold (a so- called first A5 threshold), while the signal quality of a neighboring cell exceeds a second threshold (a so-called second A5 threshold). The triggering of the A5 event causes a handover to be triggered. The A5 event is used, e.g., for intra-frequency and inter-frequency handover procedures.

[0024] In the following, a B 1 event may be defined as handover measurement event in an LTE cellular communication network (or an LTE mobile network) for inter-frequency and / or inter-RAT handover decisions. The B 1 event is triggered when the signal quality (e.g. , received signal strength or signal-to-interference-plus-noise ratio) of a neighboring cell from a different frequency band and / or RAT (e.g., 5G NR) exceeds a certain threshold (a so-called Bl thresholds). When the Bl event is triggered, the serving cell evaluates the suitability of the neighboring cell for handover based on the received signal quality. The Bl event helps facilitate seamless handovers between different frequency bands (intra-frequency handover) and / or different RATs (inter-RAT handover) to optimize network coverage, capacity, and performance.

[0025] It should be noted that any of the thresholds relating to the A2, A3, A4, A5 and Bl events may be defined separately for different frequency bands (that is, for different frequency bands of the serving cell and / or the neighboring cell, depending on the particular threshold).

[0026] In embodiments to be discussed below, a terminal device (equally called a user device, or user equipment UE) typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and / or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a cameraor video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.

[0027] A general architecture of a non-homogeneous mobile network system to which embodiments may be applied is illustrated in Figure 1. Figure 1 illustrates a simplified system architecture only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system may also comprise other functions and structures.

[0028] A non-homogeneous mobile network such as the one illustrated in Figure 1 may be defined as a mobile or cellular network whose characteristics and / or capabilities vary (i.e., are not homogeneous) across the mobile or cellular network. The non-homogeneity may relate specifically to a radio access network of the non-homogeneous mobile network. For example, in a non-homogeneous network, the coverage, capacity, technology, and services offered may differ across different regions or even within the same geographical area. The non-homogeneous mobile network may employ a particular radio access technology (RAT) such as 5G NR or LTE. In embodiments, it is specifically assumed that the non-homogeneous mobile network is non-homogeneous at least in terms of frequency bands supported. In general, a mobile network may be equally called a mobile communication network, a cellular network or a cellular communication network.

[0029] The non-homogeneous mobile network 100 of Figure 1 comprises first, second and third access nodes 101, 102, 103 (or equally base stations, cell sites, access points or (e / g)NodeBs) for serving terminal devices 104. The access nodes 101, 102, 103 may also be configured to communicate with one another over wired and / or wireless links. The access nodes 101, 102, 103 are further connected to a core network (not shown in Figure 1). Specifically, depending on the system, the core network node or element connected to the access nodes 101, 102, 103 may be, for example, a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME).

[0030] The first, second and third access nodes 101 , 102, 103 of the non-homogeneous mobile network 100 operating at partially different frequency bands. In the example of Figure 1, the first access node 101 operates at a low frequency band / jow, a medium or mid frequency band fmiC[ and a high frequency band high, the first access node 101 operates only at the high frequency band high and the third access node 103 operates at the low frequency band / jowand the high frequency band / high- For example, if the non-homogeneous mobile network is a 5G NR mobile network (i.e., the non-homogeneous mobile network support 5G NR radio access technology), the low, medium and high frequency bands may be, for example, an NR 700 frequency band at 700 MHz (e.g., an n28 band), an NR 2100 frequency band at 2100 MHz (e.g., an nl band) and an NR 3500 frequency band at 3500 MHz (e.g., an n78 band), respectively.

[0031] The first, second and third access nodes 101, 102, 103 are capable of serving terminal devices 104 at least using respective first, second and third cells 111, 112, 113. In the illustrated example, each of the first, second and third access nodes 101, 102, 103 serve terminal devices via three sectors 121 to 123, 124 to 126, 127 to 129.

[0032] Figure 1 depicts an exemplary scenario where a terminal device 104 is moving along a path or route indicated with dashed line from the first cell 101 via the second cell 112 to the third cell 113. It may be assumed that initially the terminal device 104 is connected to the first access node 101, i.e., it is being served by the sector 123 of the first cell 111. While the terminal device 104 travels through the second cell 112 of the second access node 102, the terminal device 104 might, however, never be connected to the second access node 102 in the scenario illustrated in Figure 1, assuming conventional global parameter settings are employed in the mobile network for triggering inter-frequency measurements and an inter-frequency handover (IFHO) (i.e., for triggering so-called A2 and A3 events in the case of a 5G NR network). Global parameters may be defined as parameters which are constant (i.e., homogenous) throughout the mobile network. Namely, if the terminal device 104 is initially being served using the low frequency band (e.g., the NR700 layer) by the first access node 101, it is possible that inter- frequency measurements are never started in the second cell 112 for the terminal device 104 due to the high signal levels on NR700 layer (e.g., the A2 threshold is never triggered). This high signal level is due to the fact that, as is commonly understood, a signal level of a propagating radio signal decreases (or attenuates) much faster as a function of distance at higher frequencies compared to low frequencies. Hence, becausethe second access node 102 operates only using the high frequency band (e.g., NR2100 or NR3500), the terminal device may never be triggered to measure it (and, thus, no interfrequency handover with the second access node 102 is performed). Instead, the terminal device 104 is more likely to carry out an intra-frequency handover, transitioning from the sector 123 of the first cell 101 directly to the sector 128 of the third cell 113 which also supports the low frequency band or layer (e.g., NR 700). This behavior is problematic due to the fact that typically the low frequency band has also a lower bandwidth compared to the high frequency band (e.g., 10 MHz, as opposed to 100 MHz which is a typical bandwidth for the high frequency band). Consequently, the high frequency band, which is now ignored, is usually able to provide a much better user throughput compared to the low frequency band.

[0033] The problem described above could be overcome by increasing the level of the threshold for triggering inter frequency measurements (e.g., a sector-specific A2 threshold). However, as the triggering of the inter frequency measurements (i.e., triggering of the A2 event) leads to a configuration of a measurement gap for the associated terminal device (during which the terminal device is unable to receive or transmit data) leading a reduction in user throughput, it is also important to minimize the number of unnecessary interfrequency measurement events. The throughput degradation resulting from the measurement gap is typically in the order of 12-25%.

[0034] The problem relating to measurement gaps described above could be overcome specifically in areas where the low frequency band has continuous coverage by fully disabling measurement gaps (and thus also inter-frequency measurements). Namely, the mobility could take place in such cases on, e.g., the NR700 frequency layer. When a higher frequency band from the same sector would become available, carrier aggregation could add carrier(s) on higher frequency layers, and the terminal device could, thus, benefit from the increased throughput. However, in areas where the low frequency band is missing such as in the second cell 112 of the scenario of Figure 1, this type of solution is not optimal as it would mean that the second cell 112 supporting only a high frequency band may be ignored.

[0035] The embodiments to be discussed below seek to overcome or at least alleviate the aforementioned problem by enabling the terminal device to employ cell-specific or sector-specific parameters (namely, thresholds) for triggering inter-frequency measurements and / or triggering inter-frequency handover.

[0036] In embodiments to be discussed below, it assumed that a first non- homogeneous mobile network employing a first RAT (e.g., 5G NR) such as the non- homogeneous mobile network 100 of Figure 1 coexists with a second (non-homogeneous or homogeneous) mobile network employing a second RAT (e.g., LTE). One example of this co-existence is shown in Figure 2. The example of Figure 2 is limited showing the first cell 111 of the first non-homogeneous mobile network 100 (as shown also in Figure 1) and an overlapping second cell 211 of the second mobile network as these cells 111, 211 are especially pertinent for subsequent discussion of embodiments. However, it should be understood that similar co-existence may exist also in other parts of the first and second mobile networks. In Figure 2, the elements of the first mobile network (i.e., of the first RAT) are shown with dashed lines, and the elements of the second mobile network (i.e., of the second RAT) are shown with solid lines.

[0037] In Figure 2, there is provided a first access node 101 of the first (non- homogeneous) mobile network capable of serving terminal devices at least using a first cell 111 of the first RAT and associated three sectors 121, 122, 123, and a first access node 201 of the second mobile network capable of serving terminal devices at least using a first cell 211 of the second RAT and associated three sectors 221, 222, 223. The first access node 101 supports low, medium and high frequency bands ( / jowmid high) = Cfiowi midi highi) of the first RAT, and the second access node 201 supports at least a low frequency band of the second RAT f[Ow2- In the example of Figure 2, at least one (or all) of the three sectors 121, 122, 123 of the first RAT overlaps in terms of location (e.g., coordinates), antenna bearing (i.e., an angular range covered by the sector) and supported low frequency band with respective three sectors 221, 222, 223 of the second RAT. Thus,lowl* / iow2may apply. Consequently, the radio measurements carried out in one of such substantially overlapping cells may be used for deriving information on radio conditions in the other cell.

[0038] Figure 3 illustrates a process according to embodiments for cell-specific measurement-based optimization of frequency layering. Specifically, the process of Figure 3 may be used for adjusting a trigger for inter frequency measurements in a “problematic” cell. Said “problematic” cell may correspond particularly to the first cell 101 of Figures 1 & 2 or to an analogous cell. The process of Figure 3 may be carried out, for example, by a (core) network node or a server computer comprised in or connected to a core network of a first cellular communication network (being, e.g., a 5G NR cellular communicationnetwork). In the following, the entity carrying out the process is called an apparatus for simplicity.

[0039] Referring to Figure 3, the apparatus determines, in block 301, a first sector of a first cell of a first cellular communication network which uses a first RAT. Here and in the following, a cellular communication network may be equally called a cellular network, a mobile communications network or a mobile network. The first sector is assumed to support at least a first low frequency band of the first RAT. In other words, the first sector is assumed to support a first low band frequency layer of the first RAT. Moreover, the first sector is assumed to have at least one neighboring cell (or at least one neighboring sector) of the first cellular communication network supporting a high frequency band of the first RAT (i.e., a high band frequency layer of the first RAT) but not supporting the first low frequency band of the first RAT (i.e., a first low band frequency layer of the first RAT). In other words, the first cellular communication network is assumed to be non-continuous in the vicinity of the first sector in regards to the first low frequency. The first sector may be, for example, the sector 123 of Figures 1 and 2 which has a neighboring cell 112 supporting the high frequency band of the first RAT but not the first low frequency band of the first RAT. The first low frequency band may be defined as a frequency band existing at lower frequencies compared to the high frequency band. The first cellular communication network may be a non- homogeneous standalone cellular communication network based on the first RAT.

[0040] The determination in block 301 may be based, e.g., on information on network topology of the first cellular communication network maintained in a memory of the apparatus or in an external database.

[0041] In some embodiments, the first RAT may be 5G NR. The first cellular communication network may be a 5G NR standalone (SA) network, i.e., a network which does not rely on any legacy technologies such as LTE. In such embodiments, the first low frequency band may be, e.g., n28 (i.e., NR700) frequency band, n8 (i.e., NR900) frequency band or n3 (i.e., N1800) frequency band and / or the high frequency band may be, e.g., n34 (i.e., NR2100) or n78 (i.e., NR3500) frequency band. The first low frequency band of the first RAT (e.g., 5G NR) and the high frequency band of the first RAT may be selected such that the bandwidth of the first low frequency band is (substantially) smaller than the bandwidth of the high frequency band. The term “substantially smaller” may mean here, e.g., that the bandwidth of the first low frequency band is not more than a tenth of thebandwidth of the high frequency band (e.g., 10 MHz vs. 100 MHz) or a fifth of the bandwidth of the high frequency band (e.g., 20 MHz vs 100 MHz).

[0042] In some embodiments, the determining of the first sector in block 301 may be carried out as described below in connection with Figure 4.

[0043] The apparatus obtains, in block 302, one or more measurement reports of a second cellular communication network which uses a second RAT. The second cellular communication network is assumed co-exist with the first cellular communication network, as described above in connection with Figure 2. Each of the one or more measurement reports comprises at least results of radio measurements for a second sector of a second cell being a sector of the second cellular communication network corresponding most closely in terms of location (e.g., coordinates), antenna bearing (i.e., sector orientation or angular range covered by the sector) and supported low frequency band to the first sector. The correspondence of the first and second sectors may be assumed to satisfy certain pre-defined (minimum) conditions (e.g., in terms of relative distance, difference in antenna bearing and closeness of supported low frequency bands). Here, the second sector of the second cell may be assumed to support a second low frequency band of the second RAT which, as indicated above, may be substantially (or at least partially) aligned with the first low frequency band of the first RAT. The first and second low frequency bands may overlap at least partially with each other. The locations of the first and second sectors may correspond, here and in the following, to locations of access nodes providing said first and second sectors.

[0044] The correspondence between the first and second sectors may be known by the apparatus beforehand (i.e., it may be considered pre-defined in embodiments). In practice, the correspondences between the first sector of the first cellular communication network and one or more second sectors of the second cellular communication network may have been evaluated earlier, for example, in the following way (e.g., the apparatus itself or some other network entity or node). The evaluation may comprise, first, calculating, for each pair of the first sector and one of the one or more second sectors: one or more values of respective one or more location difference metrics quantifying the difference in locations of the first and second sectors (comprising, e.g., a total location difference metric or coordinate-specific location difference metrics such as x and y coordinate difference metrics),one or more values of respective one or more antenna bearing difference metrics quantifying difference in the antenna bearing of the first and second sectors (comprising, e.g., a total antenna bearing difference metric or an azimuth-specific antenna bearing difference metric and / or an elevation-specific antenna bearing difference metric), and one or more values of respective one or more low frequency band difference metrics quantifying a difference between the first and second low frequency bands in use in the first and second sectors (comprising, e.g., a total frequency band difference metric and / or one or more frequency band difference metrics quantifying difference in start, stop and / or center frequencies).

[0045] Then, the values of the one or more location difference metrics, the one or more antenna bearing difference metrics and the one or more low frequency band difference metrics for the one or more second sectors may be compared against each other to determine the closest match to the first sector. For example, a value of a total correspondence metric may be calculated based on the values of the one or more location difference metrics, the one or more antenna bearing difference metric and the one or more low frequency band difference metric for each pair formed by the first sector and one of the one or more second sectors. The value of the total correspondence metric may be calculated, for example, as a sum or a weighted sum (or other combination) of the values of the one or more location difference metrics, the one or more antenna bearing difference metrics and the one or more low frequency band difference metrics. The second sector having the smallest value of the total correspondence metric may be identified.

[0046] Additionally or alternatively, the values of the one or more location difference metrics, the one or more antenna bearing difference metrics and the one or more low frequency band difference metrics and / or the value of the total correspondence metric, for the second sector determined to correspond to the first sector or for each of the one or more second sectors, may be compared against respective pre-defined (minimum) correspondence conditions (e.g., respective pre-defined thresholds defining largest allowable differences). The second sector may be considered to correspond to the first sector (only) if all of the predefined correspondence condition(s) are satisfied (e.g., values of difference metrics are smaller than or equal to the corresponding pre-defined thresholds). Having close correspondence between the locations of the first and second sectors and antenna bearings of the first and second sector may be especially important and, thus, the pre-definedcorrespondence conditions for the location and the antenna bearing may defined to be stricter than the pre-defined condition for the supported low frequency band (as this difference may be compensated for later). For example, the highest allowed difference between the coordinates of the first and second sectors (or of associated access nodes) may be, for each coordinate (e.g., for x-coordinate & v-coordinatc), within a range of 10-50 meters, optionally 10-30 meters. Moreover, the highest allowed difference between the antenna bearings may be, for azimuth angle, for example, ±10° (or 10° considering absolute difference).

[0047] In some embodiments, the one or more measurement reports may comprise a plurality of inter-RAT measurement reports. The plurality of inter-RAT measurement reports may relate to (i.e., provide radio measurement results of) the second sector of the second cellular communication network and a plurality of potential target sectors of one or more target cells of the first cellular communication network. Namely, each of the plurality of inter-RAT measurement reports may comprise results of radio measurements for an inter- RAT pair formed by the second sector of the second cell operating at the second low frequency band of the second RAT and a potential target sector of a potential target cell of the first cellular communication network operating at the high frequency band of the first RAT.

[0048] In some embodiments, the obtaining of the one or more measurement reports in block 302 may comprise retrieving the one or more measurement reports from a database (being an internal or external database relative to the apparatus). In some embodiments, the one or more measurement reports of the second cellular communication network may have been collected and stored to the database by a dedicated (layer-3) statistics and data collector. A statistics and data collector is a device for collecting and storing data, statistics, and performance information of a radio access network. The statistics and data collector may be configured to receive measurement reports (e.g., B 1 measurement reports) from one or more access node of the second cellular communication network (e.g., periodically or regularly).

[0049] In some embodiments, the second RAT may be LTE. In such embodiments, the second low frequency band may be, for example, LTE800 frequency band (approximately matching the NR700 frequency band), and / or the one or more measurement reports of the second cellular communication network (i.e., an LTE cellular communication network) may be one or more Bl measurement reports associated with respective one or more Bl measurement events. Each of the one or more Bl measurement reports maycomprise an LTE signal level of a source sector (i.e., here the second sector substantially matching the first sector) and an NR signal level of one or more (potential) target sectors.

[0050] It should be noted that the reason why measurements of the second cellular communication network using a different RAT compared to the first cellular communication network are leveraged here is that no relevant measurements of the first cellular communication network may be available. For example, in the case where the first and second cellular communication networks are 5G NR SA and LTE networks, NR SA measurements may not be available by the nature of the system (i.e., no inter frequency measurements have been not started).

[0051] The apparatus calculates, in block 303, one or more first reference signal received power (RSRP) distributions for the second low frequency band of the second RAT at the second sector based on the one or more measurement reports of the second cellular communication network. Each of the one or more first RSRP distributions may be specific to a particular measurement report or a particular set of measurement reports (e.g., relating to the same potential target sector in the case of inter-RAT measurement reports).

[0052] In some embodiments where the one or more measurement reports comprise the plurality of inter-RAT measurement reports, the one or more first RSRP distributions may comprise a plurality of first RSRP distributions each of which is calculated based on at least one inter-RAT measurement report relating to an inter-RAT pair formed by the second sector (being a source sector) and a potential target sector (of the first cellular communication network).

[0053] The apparatus calculates, in block 304, at least based on at least some (or all) of the one or more first RSRP distributions of the second sector of the second RAT, a sectorspecific received signal strength threshold for triggering inter frequency measurements at the first sector of the first cell. The sector-specific received signal strength threshold may be considered triggered upon the received signal strength for a terminal device at the first sector falling below it (i.e., the sector-specific received signal strength threshold may be a lower threshold). The sector-specific received signal strength threshold may be specific to the first low frequency band. In embodiments where the first RAT is 5G NR, the sector- specific received signal strength threshold for triggering the inter frequency measurements at the first sector may be a sector-specific received signal strength threshold for triggering an A2 event (i.e., a sector-specific A2 threshold).

[0054] The sector- specific received signal strength threshold calculated in block 304 is assumed to be at least higher than a corresponding global threshold (i.e., a corresponding first cellular communication network wide threshold) currently in use in the first sector at the first low frequency band. In other words, the sector-specific received signal strength threshold, once configured to an access node serving the first sector and the first cell, serves to increase the likelihood that inter frequency measurements are triggered at the first sector. Namely, as the received signal strength for a terminal device in the first sector decreases, the received signal strength falls below the sector-specific received signal strength threshold before falling below the corresponding global threshold. Consequently, it becomes more likely that a handover will be carried out for a given terminal device as it moves from the first sector to a neighboring sector of another cell supporting only the high frequency band of the first RAT. Thus, the unwanted scenario discussed in connection with Figure 1 may be avoided. To give a non-limiting example, the sector-specific received signal strength threshold could be defined to have a value from -90 dBm to -80 dBm in a case where the corresponding global threshold has a value of -100 dBm.

[0055] The calculating of the sector-specific received signal strength threshold in block 304 may be carried out in multiple parts. First, the apparatus may determine one or more second RSRP distributions of the first sector of the first RAT based on one or more first RSRP distributions of the second sector of the second RAT. As mentioned above, the first and sectors may substantially correspond to each other in terms of location, antenna bearing and supported low frequency band and, thus, RSRP distributions in the first and second sectors are assumed to be substantially equal or at least closely related to each other. Then, the apparatus may calculate the sector-specific received signal strength threshold for triggering inter frequency measurements at the first sector of the first cell based on the one or more second RSRP distributions of the first sector of the first RAT (or at least one of them). For example, the sector-specific received signal strength threshold may be defined to be equal to a sum of an average of a single selected second RSRP distribution and a product of a standard deviation of the selected second RSRP distribution and a pre-defined constant. This functionality is described in further detail in connection with Figure 5.

[0056] In some embodiments (e.g., ones where the second low frequency band of the second RAT in use in the second sector substantially matches the first low frequency band of the first RAT in use in the first sector), the one or more first RSRP distributions calculated for the second low frequency band of the second RAT at the second sector is assumed, incalculations of block 304, to correspond (directly) to one or more second RSRP distributions for the first low frequency band of the first RAT at the first sector. In other words, the one or more first RSRP distribution may be assumed to be equal to the one or more second RSRP distribution for the first low frequency band of the first RAT at the first sector. In other embodiments, the apparatus calculates one or more second RSRP distributions for the first low frequency band of the first RAT at the first sector based on said at least some (or all) of the one or more first RSRP distributions, the first low frequency band of the first RAT and the second low frequency band of the second RAT. In practice, this calculation may be based on calculating a correction factor based on the first low frequency band of the first RAT and the second low frequency band of the second RAT (or different thereof) and applying this correction factor to the first low frequency band of the first RAT and the second low frequency band of the second RAT so as to account for a difference in pathloss characteristics between the first and second low frequency bands. This latter alternative is discussed in further detail in connection with Figure 4.

[0057] In some embodiments, the apparatus may further calculate, in block 304, at least based on at least some (or all) of the one or more first RSRP distributions of the second sector of the second RAT (or based on said sector-specific received signal strength threshold for triggering inter frequency measurements), a sector-specific received signal strength threshold for triggering IFHO from the first sector of the first cell (e.g., a sector-specific first A5 threshold). This functionality is described in further detail in connection with Figure 5.

[0058] The apparatus causes (or triggers), in block 305, configuring of at least an access node serving the first cell at least to use the sector-specific received signal strength threshold for triggering inter frequency measurements in the first sector (at least at the first low frequency band). The sector- specific received signal strength threshold may replace the currently configured global threshold (e.g., a global threshold for the triggering the A2 event) for the first sector at the first low frequency band. In some embodiments, not only the first sector but all sectors of the first cell may be (re)configured at least to use the same sectorspecific received signal strength threshold.

[0059] For example, the apparatus may trigger a network (management) device or node to transmit, in block 305, to the access node, at least one signal requesting (re)configuration of the access node to use the sector-specific received signal strength threshold for triggering inter frequency measurements in the first sector. The triggering ofthe network (management) device or node may comprise transmitting, by the apparatus, at least one message comprising at least the sector-specific received signal strength threshold (and identification information of the first sector and / or the first cell) to the network (management) device or node. Said network (management) device or node may be, for example, a network management system (NMS). An NMS is a platform that enables the monitoring and management of a communication network. An NMS may, for example, enable management of one or more radio access networks, one or more core networks and / or one or more transport networks. Said networks may be associated multiple technologies and / or multiple vendors. In the context of the example of Figure 1, the sector 123 of the first cell 111 may be, for example, configured, in block 305, to use the first sector-specific received signal strength threshold (i.e., a raised threshold) for triggering inter frequency measurements due to the neighboring second cell 122 failing to support the low frequency bandlow.

[0060] Subsequently, the process described in connection with blocks 301 to 305 may be repeated for another sector of the first cell of another cell of the first cellular communication network. Alternatively, the process described in connection with blocks 301 to 304 may be carried out, in parallel or one after another, for multiple (first) sectors of one or more different cells of the first cellular communication network. Thereafter, the actions described in connection with block 305 may be carried out simultaneously for a plurality of sectors of one or more cells provided by one or more access nodes, in some such embodiments. In other words, the apparatus may cause (or trigger), in block 305, configuring of one or more access nodes serving one or more first cells at least to use one or more sectorspecific received signal strength threshold for triggering inter frequency measurements in respective plurality of first sectors (even up to hundreds of sectors), at least at the first low frequency band. In some embodiments, the one or more access nodes may comprise a plurality of access nodes and / or the one or more first cells may comprise a plurality of first cells. In some embodiments, both sector-specific received signal strength thresholds for triggering inter frequency measurements and for triggering IFHO may be configured to the one or more access nodes serving the one or more first cells associated with the plurality of first sectors.

[0061] Figure 4 illustrates a process according to embodiments for determining a first sector of a first cellular communication network around which the network is discontinuous in regards to a low frequency band of a first RAT, as described previously in connectionwith block 301 of Figure 3. In other words, the process of Figure 4 corresponds to one detailed embodiment for implementing the process of block 301 Figure 3. Thus, any of the definitions provided in connection with Figure 3 may apply, mutatis mutandis, also here. The process of Figure 4 may be carried out, for example, a (core) network node or a server computer comprised in or connected to a core network of a first cellular communication network (being, e.g., a 5G NR cellular communication network). In the following, the entity carrying out the process is called an apparatus for simplicity.

[0062] Referring to Figure 4, the apparatus, first, identifies, in block 401, a candidate cell of the first cellular communication network supporting a low frequency band of the first RAT and a candidate sector of the candidate cell. In other words, the apparatus first identifies a low-frequency-band cell and an associated low- frequency-band cell around which the first cellular communication network may or may not be continuous in regards to the first low frequency band. This low-frequency-band sector and / or cell may support also other (e.g., higher) frequency bands.

[0063] Then, the apparatus determines, in block 402, a network topology (i.e., at least cells and / or sectors and their supported frequency bands) of the first cellular communication network in a vicinity of the candidate sector. The expression “a network topology of the first cellular communication network in the vicinity of the candidate sector” may mean here the network topology of the first cellular communication network within a pre-defined distance from the candidate sector within an angular range defined by the candidate sector (or specifically its antenna bearing) or the network topology of the first cellular communication network for any neighboring sector(s) and / or any neighboring cell(s) of the candidate sector at least within an angular range defined by the candidate sector (or specifically its antenna bearing).

[0064] The apparatus determines, in block 403, based on the network topology, whether at least one of one or more neighboring cells of the candidate sector fails to support the low frequency band of the first RAT. Alternatively, the apparatus may determine, in block 403, based on the network topology, whether at least n closest cells of the candidate sector fail to support the low frequency band of the first RAT, where n is a pre-defined positive integer. The determination in block 403 may be limited to an angular range of the first sector (e.g., neighboring cells behind the first sector may not be considered).

[0065] If the result of the determination in block 403 is positive, the apparatus selects, in block 404, the candidate sector as the first sector to be processed (i.e., to which the subsequent process is directed). Thereafter, the apparatus carries out, in block 405, at least the actions described previously in connection with blocks 302 to 305. It should be noted that the processes described in connection with Figure 4 may also be combined with any of the embodiments to be discussed below.

[0066] If the result of the determination in block 403 is negative, the apparatus may repeat the process of blocks 401 to 403 for another candidate sector.

[0067] Figure 5 illustrates a process according to embodiments for sector-specific measurement-based optimization of frequency layering. Specifically, the process of Figure 5 may be used for adjusting a trigger for inter frequency measurements as well as a trigger for inter frequency handover in a “problematic” cell. Said “problematic” cell may correspond particularly to the first cell 101 of Figures 1 & 2 or to an analogous cell. The process of Figure 5 may be carried out, for example, by a (core) network node or a server computer comprised in or connected to a core network of a first cellular communication network (being, e.g., a 5G NR cellular communication network). In the following, the entity carrying out the process is called an apparatus for simplicity.

[0068] The process of Figure 5 may be considered one more detailed implementation of the process of Figure 3. Thus, any of the features and definitions provided in connection with Figure 3 may apply, mutatis mutandis, for the process of Figure 5.

[0069] Referring to Figure 5, the initial steps pertaining to blocks 501, 502, 503 may correspond fully to steps described in connection with blocks 301, 302, 303 of Figure 3 and are, thus, not repeated here for brevity.

[0070] As was described above in connection with Figure 1, the one or more measurement reports obtained in block 502 may also here comprise a plurality of inter-RAT measurement reports relating to the second sector of the second cellular communication network and a plurality of potential target sectors of one or more target cells of the first cellular communication network. Each of the plurality of inter-RAT measurement reports may comprise results of radio measurements for an inter-RAT pair formed by the second sector of the second cell operating at the second low frequency band of the second RAT and a potential target sector of a potential target cell of the first cellular communication networkoperating at the high frequency band of the first RAT. Moreover, the one or more first RSRP distributions calculated in block 503 may comprise a plurality of first RSRP distributions each of which is calculated based on at least one inter-RAT measurement report relating to an inter-RAT pair formed by the second sector (being a source sector) and a potential target sector (of the first cellular communication network).

[0071] After the calculating of the one or more first RSRP distributions for the second low frequency band of the second RAT (e.g., LTE) at the second sector based on the one or more measurement reports in block 503, the apparatus calculates, in block 504, one or more second RSRP distributions for the first low frequency band of the first RAT (e.g., 5G NR) at the first sector by applying a correction factor to the one or more first RSRP distributions. Here, the correction factor is defined, based on the first low frequency band of the first RAT and the second low frequency band of the second RAT, so as to account for a difference in pathloss characteristics between the first and second low frequency bands. For example, the correction factor may be defined based on the center frequencies and / or start and stop frequencies of the first and second low frequency bands. Use of the correction factor provides the technical advantage that the real RSRP distribution for the first low frequency band of the first RAT at the first sector may be estimated more accurately (compared to the alternative where the second RSRP distributions for the first low frequency band of the first RAT at the first sector are assumed to be equal to the first RSRP distributions for the second low frequency band of the second RAT at the second sector).

[0072] Similar to as described for the one or more first RSRP distributions, the one or more second RSRP distributions calculated in block 504 may comprise a plurality of second RSRP distributions each of which is specific to a particular inter-RAT pair formed by the second sector (being a source sector) and a potential target sector (of the first cellular communication network).

[0073] In some embodiments, the correction factor may be applied in block 504 only in response to determining that the first and second low frequency ranges fail to satisfy one or more pre-defined conditions for similarity. The one or more pre-defined conditions may comprise, for example, a first pre-defined threshold for a difference in center frequencies of the first and second low frequency ranges and / or a second pre-defined threshold for a difference in bandwidths of the first and second low frequency bands. If the first and second low frequency ranges satisfy the one or more pre-defined conditions for similarity, the oneor more first RSRP distributions for the second low frequency band of the second RAT at the second sector may be used directly as the one or more second RSRP distributions for the first low frequency band of the first RAT at the first sector, as was described also in connection with Figure 3.

[0074] The apparatus calculates, in block 505, one or more potential target sector specific received signal strength thresholds for triggering inter frequency measurements at the first sector (at the first low frequency band) based, respectively, on the one or more second RSRP distributions. Here, a potential target sector specific received signal strength threshold for a second RSRP distribution may be defined to be equal to one of- a sum of an average of the second RSRP distribution and a standard deviation of the second RSRP distribution,- a sum of an average of the second RSRP distribution and a product of a standard deviation of the second RSRP distribution and a pre-defined constant,- a mth percentile of the second RSRP distribution, wherein m is a pre-defined real number larger than 50 and smaller than 100 (e.g., m = 70), or- a sum (e.g., in decibels) of an average of the second RSRP distribution and a pre-defined value.

[0075] The apparatus determines, in block 506, a first sector-specific received signal strength threshold (i.e., the “sector-specific received signal strength threshold” of previous embodiments) for triggering the inter frequency measurements at the first sector based on the one or more potential target sector specific signal strength thresholds. The first sectorspecific received signal strength threshold may be specific to the first low frequency band. For example, the apparatus may determine, in block 506, the first sector-specific received signal strength threshold to be equal to a maximum of the one or more potential target sector specific received signal strength thresholds. As described above, the first sector- specific received signal strength threshold may be, e.g., a sector-specific A2 threshold (for the first low frequency band). If the number of first RSRP distributions (and thus also the number of second RSRP distributions and the one or more potential target sector specific received signal strength thresholds) is equal to one, block 506 may be omitted.

[0076] The apparatus determines, in block 507, based on the first sector-specific received signal strength threshold for the triggering of the inter frequency measurements at the first sector, a second sector-specific received signal strength threshold for the first sectorfor triggering an IFHO from the first sector of the first cell to a target sector of a target cell. The second sector-specific received signal strength threshold may be considered triggered upon the received signal strength for a terminal device at the first sector falling below it (i.e., the second sector-specific received signal strength threshold may be a lower threshold). The second sector-specific received signal strength threshold may be one of one or more conditions which need to be satisfied for triggering the IFHO. For example, the second sector-specific received signal strength threshold for the first sector for triggering the IFHO may be determined to be equal to the first sector-specific received signal strength threshold or to a sum of the first sector-specific received signal strength threshold (in decibels) and a pre-defined constant. The second sector-specific received signal strength threshold may be defined to be at least higher than a corresponding global threshold (for triggering an IFHO) currently in use in the first sector.

[0077] In embodiments where the first RAT is 5G NR, the second sector- specific received signal strength threshold for triggering the IFHO may be a first A5 threshold for received signal strength at the first sector (and at the first low frequency band). As described above, the first A5 threshold is a 5G NR (lower) threshold for signal quality (e.g., received signal strength or signal-to-interference-plus-noise ratio) of a serving cell with one condition for triggering an A5 event being that the signal quality of the serving cell becomes worse than the first A5 threshold. In some embodiments, the first A5 threshold may be determined in block 507 to be equal to the second sector- specific received signal strength threshold for the triggering of the inter frequency measurements at the first sector (which may correspond to a sector-specific A2 threshold). The second A5 threshold for the neighboring cell (and at the high frequency band of the first RAT) may have a pre-defined value. This pre-defined may value be defined, e.g., to be equal to a sum of the global A2 threshold for the high frequency band of the first RAT and a hysteresis-related constant. To give a concrete nonlimiting example, the (sector-specific) A2 threshold could be defined, for example, to be equal to -85 dBm while the (sector-specific) first A5 threshold could also be defined to be equal to -85 dBm. The second A5 threshold for the neighboring cell could have a pre-defined value of -95 dBm, for example. This value assumes that the global A2 threshold is equal to -100 dBm, and the hysteresis is equal to 5 dBm.

[0078] In some alternative embodiments where the first RAT is 5G NR, the second sector-specific received signal strength threshold for triggering the IFHO may be an Ad- event threshold.

[0079] The apparatus causes (or triggers), in block 508, configuring of an access node serving the first cell at least to use the first sector-specific received signal strength threshold for triggering inter frequency measurements in the first sector and to use the second sectorspecific received signal strength threshold for triggering the IFHO from the first sector. In both cases, the configuration may pertain at least to the first low frequency band.

[0080] In some embodiments, only one or two of the three features described in connection with block 504, blocks 505 to 506 & block 507, respectively, may be implemented in connection with any of the processes of Figures 3 to 4.

[0081] Figure 6 illustrates a process according to embodiments for sector-specific measurement-based optimization of frequency layering. Specifically, the process of Figure 6 may be used for adjusting a trigger for inter frequency measurements as well as a trigger for inter frequency handover in a “problematic” cell. Said “problematic” cell may correspond particularly to the first cell 101 of Figures 1 & 2 or to an analogous cell. The process of Figure 6 may be carried out, for example, by a (core) network node or a server computer comprised in or connected to a core network of a first cellular communication network (being, e.g., a 5G NR cellular communication network). In the following, the entity carrying out the process is called an apparatus for simplicity.

[0082] The process of Figure 6 may be considered one more detailed implementation of the process of Figure 3. Thus, any of the features and definitions provided in connection with Figure 3 may apply, mutatis mutandis, for the process of Figure 6.

[0083] Referring to Figure 6, the initial steps pertaining to blocks 601, 602, 603 may correspond to steps described in connection with blocks 301, 302, 303 of Figure 3. However, in this case, as was described above in connection with Figure 1 as an optional feature, a plurality of measurement reports are obtained in block 602 and further these plurality of measurement reports are assumed to comprise (or consist of) a plurality of inter-RAT measurement reports relating to the second sector of the second cellular communication network and a plurality of potential target sectors of one or more target cells of the first cellular communication network. Each of the plurality of inter-RAT measurement reports may comprise results of radio measurements for an inter-RAT pair formed by the second sector of the second cell operating at the second low frequency band (e.g., LTE800) of the second RAT and a potential target sector of a potential target cell of the first cellular communication network operating at the high frequency band (e.g., NR3500) of the firstRAT. Altogether, the plurality of inter-RAT measurement reports may relate to (i.e., provide radio measurement results on) a plurality of such inter-RAT pairs. Moreover, a plurality of first RSRP distributions are calculated in block 603 and these plurality of first RSRP distributions are assumed to comprise (or consist of) a plurality of first RSRP distributions each of which is calculated based on at least one inter-RAT measurement report relating to an inter-RAT pair formed by the second sector and a potential target sector (of the first cellular communication network).

[0084] After the calculating of the plurality of first RSRP distributions for the second low frequency band of the second RAT (e.g., LTE) at the second sector based on the plurality of inter-RAT measurement reports in block 603, the apparatus selects, in block 604, from the plurality of first RSRP distributions, a subset of first RSRP distributions. The subset of first RSRP distributions may relate to (i.e., comprise first RSRP distributions associated with) inter-RAT pairs comprising the n potential target sectors (for IFHO) for which most measurement samples are available. In other words, each of said inter-RAT pairs comprises the first sector and one of the n potential target sectors for IFHO. Here, n is a pre-defined positive integer. In some embodiments, n may be larger than or equal to 5 and / or smaller than or equal to 20. For example, n may be equal to 10.

[0085] In practice, the selecting of the subset of first RSRP distributions in block 604 may comprise, in some embodiments, ordering the plurality of first RSRP distributions based on the number of measurement samples available (i.e., based on how many measurement samples were used for calculating the associated first RSRP distribution), and selecting the subset of first RSRP distributions based on the ordered plurality of first RSRP distributions.

[0086] The functionality described in connection with block 604 provides the technical advantage that the processing load relating to the subsequent steps of the process is reduced due to the reduced number of first RSRP distributions that need to be considered. Also, the first RSRP distributions which are based on only a few measurement samples may not be dependable (i.e., they may not accurately reflect the real RSRP distribution) and, thus, by removing or filtering out such first RSRP distributions, the subsequent processing steps are made more accurate.

[0087] The apparatus calculates, in block 605, the (first) sector-specific received signal strength threshold (e.g., the sector-specific A2 threshold) for triggering inter frequency measurements at the first sector of the first cell based on the subset of first RSRPdistributions. This step may be carried out as described previously in connection with block 303 of Figure 3 and / or blocks 503 to 506 though with the starting point being, in this case, the subset of first RSRP distributions (as opposed to all first RSRP distributions available). Thus, for example, the (first) sector-specific received signal strength threshold for triggering inter frequency measurements may be calculated by first calculating a set of second RSRP distributions for the first sector and the first low frequency band of the first RAT based on the subset of first RSRP distributions (e.g., by using a correction factor) and, thereafter, calculating the sector-specific received signal strength threshold for triggering inter frequency measurements at first sector of first cell based on the set of second RSRP distributions.

[0088] The apparatus may optionally also determine a second sector-specific received signal strength threshold (e.g., the first A5 threshold) for triggering IFHO, similar to as described in connection with block 507 of Figure 5.

[0089] Then, the apparatus calculates, in block 606, based on at least some (or all) of the plurality of inter-RAT measurement reports, a plurality of third RSRP distributions for the high frequency band of the first RAT (e.g., NR) at a plurality of potential target sectors of the plurality of inter-RAT pairs. Here, the plurality of inter-RAT pairs are inter-RAT pairs to which the plurality of inter-RAT measurement reports relate.

[0090] The apparatus determines, in block 607, whether any eligible target sector for IFHO from the first sector (or from the first cell) exists based on the plurality of third RSRP distributions. Here, the eligible target sectors are sectors satisfying one or more pre-defined performance criteria at the high frequency band of the first RAT. Thus, in embodiments where the first RAT is 5G NR, the apparatus may determine, in block 607, whether any eligible NR high band target sectors exist for the IFHO.

[0091] In some alternative embodiments, the determining of block 607 may be carried out per target cell, that is, the apparatus may determine, in block 607, whether any eligible target cells for IFHO from the first cell exists based on the plurality of third RSRP distributions, where the eligible target cells are cells satisfying one or more pre-defined performance criteria at the high frequency band of the first RAT

[0092] In some embodiments, the one or more pre-defined performance criteria comprise a pre-defined threshold for a particular (measurement-based performance) metric.Said metric may be, for example, equal to an average RSRP at a potential target sector (or cell) at the high frequency band of the first RAT. Alternatively, said metric may be equal to a sum of an average RSRP and a standard deviation of the RSRP at a potential target sector (or cell) at the high frequency band of the first RAT. In this case, the pre-defined threshold may, for example, have a value of -100 dBm. According to a further alternative, said metric may be equal a sum of an average RSRP and a product of a standard deviation of the RSRP and a pre-defined constant at a potential target sector (or cell) at the high frequency band of the first RAT.

[0093] If at least one any eligible target sector (or cell) for IFHO is found in block 607, the first sector may be considered suitable for sector-specific reconfiguration. Thus, if the determination in block 607 provides a positive result, the apparatus causes (or triggers), in block 608, configuring an access node serving the first cell (and thus the first sector) to use the sector-specific received signal strength threshold (or both the first and second sectorspecific received signal strength thresholds), similar to as described in connection with previous embodiments. On the other hand, if the determination in block 607 provides a negative result (i.e., no eligible target sector is found), the process for configuring sectorspecific received signal strength threshold(s) to the first sector is effectively terminated.

[0094] The functionality described in connection with block 606 to 607 provides the technical advantage that the (re)configuration of the first sector is carried out only if it is expected that such (re)configuration is useful (i.e., it is expected to lead to an improvement in overall network service) and, thus, unnecessary (re)configuration of cells / sectors can be avoided.

[0095] In some embodiments, only one of the two features described in connection with block 604 & blocks 606 to 607, respectively, may be implemented in connection with any of the processes of Figures 3 to 5.

[0096] Figure 7 illustrates a process according to embodiments for implementing a rollback functionality for the sector-specific received signal strength threshold(s) and for inter frequency measurements altogether. The process of Figure 7 may be carried out, for example, by a (core) network node or a server computer comprised in or connected to a core network of a first cellular communication network (being, e.g., a 5G NR cellular communication network). In the following, the entity carrying out the process is called an apparatus for simplicity.

[0097] Referring to Figure 7, the apparatus initially performs, in block 701, the process of any of Figures 3 to 6. In other words, it is assumed that at least a first sector of a first cell of a first cellular communication network (e.g., 5G NR) is configured to use the first and / or second sector-specific received signal strength threshold for triggering inter frequency measurements and / or IFHO. In the context of the example of Figure 1, the sector 123 of the first cell 111 may be configured use the first and / or second sector-specific received signal strength threshold for triggering inter frequency measurements and / or IFHO due to the neighboring second cell 122 failing to support the low frequency bandlow.

[0098] The apparatus is assumed monitor changes in the network topology of the first cellular communication network. These changes may comprise, for example, addition and / or removal of access nodes and / or cells and / or sectors and / or changes in parameters employed by the access nodes of the first cellular communication network (e.g., changes in supported frequency bands). Two different checks (blocks 702, 703 & blocks 704, 705) are carried out (e.g., periodically or regularly) based on the monitoring.

[0099] In response to detecting a change in the network topology of the first cellular communication network indicating that all neighboring sectors of the first sector (or at least all neighboring sectors of the first sector within an angular range of the first sector) now support the first low frequency band of the first RAT (i.e., no discontinuity regarding low frequency band coverage no longer exists) in block 702, the apparatus carries out, in block 703, rollback to revert from any configured sector- specific received signal strength threshold (at the first sector) to a corresponding (default) global threshold. In other words, the apparatus causes or triggers reconfiguration of an access node serving the first sector of the first cell to revert to using the (default) global threshold(s) for triggering inter frequency measurements and / or IFHO as the use of sector-specific received signal strength threshold is no longer necessary.

[0100] In the context of the example of Figure 1, the operation of blocks 702, 703 could mean, for example, that a support for the low frequency band ( / jow) has been recently added to the second cell 112 neighboring the first cell (which is assumed here to have been configured to employ first and / or second sector-specific received signal strength threshold). Thus, there is no reason anymore to employ the first and / or second sector-specific received signal strength threshold for the sector 123 of the first cell 111, instead of corresponding global thresholds.

[0101] In response to detecting a change in the network topology of the first cellular communication network indicating that the first cellular communication network is now (fully) uniform (or equally homogeneous) for the first sector of the first cellular communication network and k sectors of the first cellular communication network closest (in distance) to the first sector in block 704, the apparatus causes or triggers, in block 705, disabling of inter frequency measurements (and thus of associated measurement gaps) at least at the first sector. Here, k is a pre-defined positive integer (e.g., 1, 2 or 3). In other words, the apparatus causes or triggers reconfiguration of an access node serving the first cell to disable inter frequency measurements as they are no longer useful.

[0102] In some embodiments, the check of block 704 may be carried out per cell (as opposed to per sector). In other words, the apparatus may detect a change in the network topology of the first cellular communication network indicating that the first cellular communication network is now (fully) uniform for the first cell of the first cellular communication network and k cells of the first cellular communication network closest (in distance) to the first cell.

[0103] In some embodiments, the disabling of the inter frequency measurements in block 705 may not be limited to the first sector of the first cell. Namely, in some embodiments, the disabling may be applied also, e.g., at any sectors of the first cell other than the first sector and / or at said k sectors closest to the first sector (or said k cells closest to the first cell). Additionally or alternatively, the disabling may be applied also at one or more cells (or one or more sectors) of the second cellular communication network using the second RAT (e.g., LTE). For example, the disabling of the inter frequency measurements may be applied at the second sector of the second communications network co-located (i.e., at least partially overlapping) with the first sector of the first cellular communication network and / or / sectors closest to said second sector of the second cellular communication network. Alternatively, the disabling of the inter frequency measurements may be applied at one or more cells of the second communications network co-located (i.e., at least partially overlapping) with the first cell of the first cellular communication network and / or / cells closest to said one or more cells of the second cellular communication network.

[0104] In the context of the example of Figure 1, the operation of blocks 704, 705 could mean, for example, that a support for the low and medium frequency bands ( / low& / mid) has been recently added to the second cell 112, and a support for the medium frequencybands ( / mid) has been recently added to the third cell 113. Thus, the first cellular communication network of Figure 1 is now fully uniform (i.e., homogeneous) as the first, second and third cells 111, 112, 113 all support the same frequency bands of the first RAT. Thus, the apparatus may disable inter frequency measurements at least at the sector 123 and optionally at the other sectors 121, 122 of the first cell 111 and / or at least some of sectors 124 to 129 of the second and / or third cells 112, 113.

[0105] In some alternatives embodiments, any of the actions described in connection with any of Figures 3 to 7 may be carried out per cell (i.e., cell-specifically), as opposed to per sector of a cell (i.e., sector-specifically). Thus, instead of a first and / or second sectorspecific received signal strength thresholds, there may be defined first and / or second cellspecific received signal strength thresholds.

[0106] The blocks, related functions, and information exchanges described above by means of Figures 3 to 7 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between them or within them, and other information may be sent, and / or other rules applied. Some of the blocks or part of the blocks or one or more pieces of information can also be left out or replaced by a corresponding block or part of the block or one or more pieces of information.

[0107] Figures 8 to 10 illustrate measurements results relating to a measurement campaign (i.e., a drive test) carried out in a trial area in Espoo, Finland. In the measurement campaign, network measurements were conducted in the trial area before and after executing the process according to an embodiment for configuring sector-specific received signal strength thresholds for triggering inter frequency measurements (namely, a sector-specific A2 thresholds) and sector-specific received signal strength thresholds for triggering IFHO (namely, a sector-specific first A5 threshold). In the “before” case, the (default) global values for the A2 and A5 thresholds were employed. The process according to the embodiment is, in particular, a process implementing all features of Figures 3 to 6 in this example. The network measurements were carried out for both a 5G NR & LTE non- standalone (NS A) mobile network and a 5G NR standalone (SA) mobile network.

[0108] Figure 8 illustrates pre-drive time series throughput in the pilot cluster for the 5G NSA and SA mobile networks (i.e., throughput before configuring sector-specific A2 & A5 thresholds) while Figure 9 illustrates post-drive time series throughput in the pilot clusterfor a 5G NSA and SA mobile networks (i.e., throughput after configuring sector-specific A2 & A5 thresholds). Specifically, Figures 8 & 9 plot the average total throughput in Mbps (vertical axis) against time (horizontal axis). The same UE route was employed in all measurements of Figures 8 & 9.

[0109] Similar problematic behavior as discussed in connection with Figure 1 may be observed from the results of the conventional 5G NR SA network (employing global A2 and A5 thresholds) in Figure 8. Namely, black circles are used in Figure 8 for highlighting areas where the UE connected to the 5G NR SA mobile network got “stuck” on NR700 layer, and, consequently, throughput was very poor, even less than 10 Mbs. Notably, this problematic behavior is not observed in the NSA (ETE + NR) results of Figure 8. On the other hand, it may be observed that the problematic behavior is no longer present in the results of the 5G NR SA network after it has been configured to employ the sector-specific A2 and A5 thresholds in Figure 9. Instead, in this case, the UE is handed over to the NR3500 cell and throughput is increased dramatically, as a consequence, especially in the areas indicated with black circles.

[0110] Figure 10 illustrates a cumulative distribution function (CDF) of downlink (DE) throughput for the 5G NR SA mobile network before and after it has been configured to employ the sector-specific A2 and A5 thresholds. As can be observed from Figure 10, the 5G NR SA mobile network provides much better performance following the configuration of the sector-specific A2 and A5 thresholds. For example, a median throughput (shown with a dashed line) is increased from relatively low 20 Mbs up to 140 Mbps. This result is from the pilot cluster, where the performance was particularly poor. In larger scale city level tests, downlink improvements of around 30-40% and uplink improvements of 60-70% in terms of throughput have been achieved.

[0111] Figure 11 provides an apparatus 1101 according to some embodiments. Specifically, Figure 11 may illustrate an apparatus configured to carry out at least the functions described above in connection with triggering configuring of access node to employ sector-specific received signal threshold(s) at least for triggering inter frequency measurements. The apparatus 1101 may be, e.g., a server computing device or a server system. In some embodiments, the apparatus 1101 may be a cloud server. The apparatus 1101 may be comprised in or (communicatively) connected to a core network of a first and / or second cellular communication network (e.g., 5G NR (SA) network and / or ETE network).

[0112] The apparatus 1101 may comprise one or more control circuitry 1120, such as at least one processor, and at least one memory 1130, including one or more algorithms 1131, such as a computer program code (software) wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus 1101 to carry out any one of the exemplified functionalities of the apparatus 1101 described above in connection with Figures 3 to 7. Said at least one memory 1130 may also comprise at least one database 1132.

[0113] When the one or more control circuitry 1120 comprises more than one processor, the apparatus 1101 may be a distributed device wherein processing of tasks takes place in more than one physical unit. Each of the at least one processor may comprise one or more processor cores. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. The one or more control circuitry 1120 may comprise at least one Qualcomm Snapdragon and / or Intel Atom processor. The one or more control circuitry 1120 may comprise at least one application-specific integrated circuit (ASIC). The one or more control circuitry 1120 may comprise at least one field-programmable gate array (FPGA).

[0114] Referring to Figure 11, the one or more control circuitry 1120 of the apparatus 1101 is configured to carry out functionalities described above by means of any of elements of Figures 3 to 7 using one or more individual circuitries. It is also feasible to use specific integrated circuits, such as ASIC (Application Specific Integrated Circuit) or other components and devices for implementing the functionalities in accordance with different embodiments.

[0115] Referring to Figure 11, the apparatus 1101 may further comprise different interfaces 1110 such as one or more communication interfaces comprising hardware and / or software for realizing communication connectivity according to one or more communication protocols. Specifically, the one or more communication interfaces 1110 may comprise, for example, interfaces providing connection to a first cellular communication network (e.g., a 5G NR (SA) network) or specifically to a radio access network thereof, a second cellular communication network (e.g., an ETE network) and / or to database to which measurement results of the second cellular communication network are collected.

[0116] Referring to Figure 11, the memory 1130 may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

[0117] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software (and / or firmware), such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software, including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus, such as a terminal device or an access node, to perform various functions, and (c) hardware circuit(s) and processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g. firmware) for operation, but the software may not be present when it is not needed for operation. This definition of ‘circuitry’ applies to all uses of this term in this application, including any claims. As a further example, as used in this application, the term ‘circuitry’ also covers an implementation of merely a hard-ware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware.

[0118] In an embodiment, at least some of the processes described in connection with Figures 3 to 7 may be carried out by an apparatus comprising corresponding means for carrying out at least some of the described processes. Some example means for carrying out the processes may include at least one of the following: detector, processor (including dualcore and multiple-core processors), digital signal processor, controller, receiver, transmitter, encoder, decoder, memory, random access memory (RAM), read-only memory (ROM), software, firmware, display, user interface, display circuitry, user interface circuitry, user interface software, display software, circuit, filter (low-pass, high-pass, bandpass and / or bandstop), sensor, circuitry, inverter, capacitor, inductor, resistor, operational amplifier, diode and transistor. In an embodiment, the at least one processor, the memory, and the computer program code form processing means or comprises one or more computer program code portions for carrying out one or more operations according to any one of the embodiments of Figures 3 to 7 or operations thereof. In some embodiments, at least some of the processes may be implemented using discrete components.

[0119] Embodiments as described may also be carried out, fully or at least in part, in the form of a computer process defined by a computer program or portions thereof. Embodiments of the methods described in connection with Figures 3 to 7 may be carried out by executing at least one portion of a computer program comprising corresponding instructions. The computer program may be provided as a computer readable medium comprising program instructions stored thereon or as a non-transitory computer readable medium comprising program instructions stored thereon. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. The computer program medium may be a non-transitory medium. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art.

[0120] The term “non-transitory”, as used herein, is a limitation of the medium itself (that is, tangible, not a signal) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM).

[0121] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0122] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0123] Even though embodiments have been described above with reference to examples according to the accompanying drawings, it is clear that the embodiments are not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.INDUSTRIAL APPLICABILITY

[0124] At least some embodiments of the present invention find industrial application in cellular communications.

Claims

CLAIMS1. A computer-implemented method comprising: determining a first sector of a first cell of a first cellular communication network which uses a first radio access technology, RAT, wherein the first sector supports at least a first low frequency band of the first RAT and has at least one neighboring cell of the first cellular communication network supporting a high frequency band of the first RAT but not supporting the first low frequency band, the first low frequency band being defined as a frequency band existing at lower frequencies compared to the high frequency band; obtaining one or more measurement reports of a second cellular communication network which uses a second RAT, wherein each of the one or more measurement reports comprises at least results of radio measurements for a second sector of a second cell being a sector of the second cellular communication network corresponding most closely in terms of location, antenna bearing and supported low frequency band to the first sector; calculating one or more first reference signal received power, RSRP, distributions for a second low frequency band of the second RAT at the second sector based on the one or more measurement reports; calculating, at least based on at least some of the one or more first RSRP distributions, a sector-specific received signal strength threshold for triggering inter frequency measurements at the first sector of the first cell, wherein the sector-specific received signal strength threshold is defined to be at least higher than a corresponding global threshold currently in use in the first sector; and causing configuring at least an access node serving the first cell at least to use the sector-specific received signal strength threshold for triggering inter frequency measurements in the first sector.

2. The computer-implemented method of claim 1, wherein the determining of the first sector comprises: identifying a candidate cell of the first cellular communication network supporting a low frequency band and a candidate sector of the candidate cell; determining a network topology of the first cellular communication network in a vicinity of the candidate sector; anddetermining, based on the network topology, that at least one of one or more neighboring cells of the candidate sector fails to support the low frequency band.

3. The computer-implemented method according to any preceding claim, wherein the one or more measurement reports comprise a plurality of inter-RAT measurement reports relating to the second sector of the second cellular communication network and a plurality of potential target sectors of one or more potential target cells of the first cellular communication network, each of the plurality of inter-RAT measurement reports comprising results of radio measurements for an inter-RAT pair formed by the second sector of the second cell operating at the second low frequency band of the second RAT and a potential target sector of a potential target cell of the first cellular communication network operating at the high frequency band of the first RAT.

4. The computer-implemented method of claim 3, wherein the one or more first RSRP distributions comprise a plurality of first RSRP distributions each of which is calculated based on at least one inter-RAT measurement report relating to an inter-RAT pair formed by the second sector and a potential target sector; the computer-implemented method further comprising: selecting, from the plurality of first RSRP distributions, a subset of first RSRP distributions, wherein the subset of first RSRP distributions relates to inter-RAT pairs comprising the n potential target sectors for which most measurement samples are available, wherein n is a pre-defined positive integer; and calculating the sector-specific received signal strength threshold for triggering inter frequency measurements at the first sector of the first cell based on the subset of first RSRP distributions.

5. The computer-implemented method of claim 3 or 4, further comprising: calculating, based on at least some of the plurality of inter-RAT measurement reports, a plurality of third RSRP distributions for the high frequency band of the first RAT at the plurality of potential target sectors of a plurality of inter-RAT pairs.

6. The computer-implemented method of claim 5, further comprising:determining whether any eligible target sector for inter frequency handover, IFHO, from the first sector exists based on the plurality of third RSRP distributions, wherein the eligible target sectors are sectors satisfying one or more pre-defined performance criteria at the high frequency band; and causing the configuring of the access node only in response to determining that at least one eligible target sector exists.

7. The computer-implemented method of claim 6, wherein the one or more predefined performance criteria comprise a pre-defined threshold for a metric which is equal to:- an average RSRP at a potential target sector,- a sum of an average RSRP and a standard deviation of the RSRP at a potential target sector or- a sum of an average RSRP and a product of a standard deviation of the RSRP and a pre-defined constant at a potential target sector.

8. The computer-implemented method according to any preceding claim, wherein, in the calculating of the sector-specific received signal strength threshold for triggering the inter frequency measurements at the first sector of the first cell, the one or more first RSRP distributions calculated for the second low frequency band of the second RAT at the second sector is assumed to correspond to one or more second RSRP distributions for the first low frequency band of the first RAT at the first sector.

9. The computer-implemented method according to any of claims 1 to 7, wherein the calculating of the sector-specific received signal strength threshold for triggering inter frequency measurements at the first sector comprises: calculating one or more second RSRP distributions for the first low frequency band of the first RAT at the first sector based on said at least some of the one or more first RSRP distributions, the first low frequency band of the first RAT and the second low frequency band of the second RAT; and calculating, based on the one or more second RSRP distributions, the sectorspecific received signal strength threshold for triggering the inter frequency measurements at the first sector.

10. The computer-implemented method of claim 9, wherein the calculating of the one or more second RSRP distributions comprises: applying a correction factor to the one or more first RSRP distributions, wherein the correction factor is defined, based on the first low frequency band of the first RAT and the second low frequency band of the second RAT, so as to account for a difference in pathloss characteristics between the first and second low frequency bands.

11. The computer-implemented method according to any of claims 9 to 10, wherein the calculating of the sector-specific received signal strength threshold for triggering the inter frequency measurements at the first sector based on the one or more second RSRP distributions comprises: calculating one or more potential target sector specific received signal strength thresholds based, respectively, on the one or more second RSRP distributions, wherein a potential target sector specific received signal strength threshold for a second RSRP distribution is defined to be equal to one of:- a sum of an average of the second RSRP distribution and a standard deviation of the second RSRP distribution,- a sum of an average of the second RSRP distribution and a product of a standard deviation of the second RSRP distribution and a pre-defined constant,- a mth percentile of the second RSRP distribution, wherein m is a pre-defined real number larger than 50 and smaller than 100, or- a sum of an average of the second RSRP distribution and a pre-defined value; and determining the sector-specific received signal strength threshold for triggering the inter frequency measurements at the first sector to be equal to a maximum of the one or more potential target sector specific received signal strength thresholds.

12. The computer-implemented method according to any preceding claim, further comprising: determining, based on the sector-specific received signal strength threshold for the triggering of the inter frequency measurements at the first sector being a first sectorspecific received signal strength threshold, a second sector-specific received signal strength threshold for the first sector for triggering an IFHO from the first sector of the first cell to a target sector of a target cell,wherein the causing of the configuring of the access node further comprises causing configuring the access node to use the second sector-specific received signal strength threshold for triggering the IFHO from the first sector of the first cell.

13. The computer-implemented method of claim 12, wherein the first RAT is Fifth Generation New Radio, 5G NR, and the second sector-specific received signal strength threshold is a sector-specific first A5 threshold for received signal strength at the first sector or an A4-event threshold.

14. The computer-implemented method of claim 12 or 13, wherein the second sector-specific received signal strength threshold is determined to be equal to the first sectorspecific received signal strength threshold.

15. The computer-implemented method according to any preceding claim, further comprising: in response to detecting a change in a network topology of the first cellular communication network indicating that all neighboring sectors of the first sector now support the first low frequency band of the first RAT, carrying out rollback to revert from any configured sector-specific received signal strength threshold to a corresponding global threshold.

16. The computer-implemented method according to any preceding claim, further comprising: in response to detecting a change in a network topology of the first cellular communication network indicating that the first cellular communication network is now homogeneous for the first sector of the first cellular communication network and k sectors of the first cellular communication network closest to the first sector, causing disabling of the inter frequency measurements at least at the first sector, wherein k is a pre-defined positive integer.

17. The computer-implemented method of claim 16, wherein the disabling of the inter frequency measurements is applied also at any sectors of the first cell other than the first sector and / or the k sectors of the first cellular communication network and / or at the second sector of the second cellular communication network co-located with the first sectorof the first cellular communication network and / sectors of the second cellular communication network closest to the second sector, / being a pre-defined positive integer.

18. The computer-implemented method according to any preceding claim, wherein the first RAT is Fifth Generation New Radio, 5G NR, and the second RAT is Long- Term Evolution, LTE.

19. The computer-implemented method of claim 18, wherein the one or more measurement reports are one or more Bl measurement reports.

20. The computer-implemented method of claim 18 or 19, wherein the sectorspecific received signal strength threshold for triggering the inter frequency measurements at the first sector is a sector-specific received signal strength threshold for triggering an A2 event.

21. The computer-implemented method according to any preceding claim, wherein the first cellular communication network is a non-homogeneous standalone cellular communication network based on the first RAT.

22. An apparatus comprising means for performing the computer-implemented method according to any preceding claim.

23. The apparatus of claim 22, wherein the means comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform said computer-implemented method.

24. A computer program which, when the computer program is executed by a computing device, causes the computing device to carry out the computer-implemented method of any of claims 1 to 21.

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